1-0-alkyl-2-0-acetyl-sn-glycero-3-phosphorylcholine or platelet activating factor (PAF) is an astonishingly potent inducer of platelet aggregation and secretion in vitro and of an anaphylactic syndrome in rabbits in vivo. In preliminary studies we found this compound to be similarly potent in aggregating and degranulating neutrophils in contracting smooth muscle of lung, and in destroying normal pulmonary architecture. We propose to study further the bioactions of PAF, examine PAF release in stimulated neutrophils, and prepare and study various analogues of PAF. The in vitro bioactions of PAF will be analyzed in a broad spectrum of neutrophil, platelet, and smooth muscle spasmogenic assays which may have particular relevance to the in vivo toxicity of this compound. Additionally, we plan to examine the role of arachidonic acid metabolism, calcium fluxes, putative intracellular acetylating reactions, and specific cell-associated receptors in the neutrophil response to PAF. The in vivo bioactions of PAF will employ a previously described in vivo and ex vivo isolated, perfused rabbit lung model in order to measure the ability of PAF to cause neutropenia/thrombocytopenia; stasis of blood cells in lung vasculature, respiratory dysfunction, and histologic lung damage (as determined using light, scanning, and transmission electron microscopy). PAF analogues will be prepared by direct organic synthesis and similarly assayed. Finally, studies on PAF generation will employ biochemical and enzymatic techniques in order to determine the mechanisms, precursors, intermediates, and metabolic pathways involved in the synthesis and release of this lipid in the stimulated neutrophil. These studies, then, attempt to understand the mechanisms of production and action of an endogenously-formed, potential toxin. Because human tissues produce and respond to PAF, these studies may be relevant to various conditions involving unexplained acute pulmonary dysfunction in patients.